In a disc brake, the brake caliper is generally arranged straddling the outer peripheral margin of a brake disc, adapted to rotate about a rotation axis defining an axial direction. In a brake disc, a radial direction, which is substantially orthogonal to said axial direction, and a tangential or circumferential direction, orthogonal to both said axial direction and said radial direction, is further defined, to form a substantially cylindrical coordinate system.
The known brake calipers are generally provided with pads adapted to engage a braking band of the brake disc associable with the brake caliper to cause the deceleration of the vehicle on which the brake caliper is installed. The pads may be replaced by pins, connected to the brake caliper body, and may thus comprise eyelets, in which the pins are inserted with clearance, so as to allow the pads to slide along them, when they are subjected to the action of the specific thrust means.
According to a known type of pads, the pins also have the function of transmitting the braking force to the brake caliper itself, rather than allowing the pads to abut with a side thereof on the brake caliper to relieve such a braking action.
The plate of such a type of pads comprises a pair of side ears, which extend laterally in tangential direction, in which eyelets are provided intended to accommodate the pins. Said side ears are usually made on a radially inner portion of the plate.
The eyelets usually display a square shape with rounded or beveled angles. The pins which support the pads, instead, usually have circular section cylindrical shape. The distance and the size of the eyelets and the pins are chosen so that, during the braking action, the pad is pulled and transmits the braking force to the pin arranged on the inlet side of the brake disc, in the gap between the pads, while the pin arranged on the outlet side of the disc implements a radial resting.
In particular, the eyelets and the pins are shaped so that, during the braking action, the mutual contact between the pin to which the braking force is transmitted and the eyelet substantially occurs in two contact points, in particular a first contact point, in which the pin supports the pad, and a second contact point, in which the braking force is transmitted to the pin during braking.
Pads which can be related to the aforesaid category are shown, for example, in documents US-2011-226566 and US-2012-043168.
However, such solutions have some drawbacks.
Indeed, as soon as the braking is triggered, the pad is free to move and to accelerate by virtue of the clearance with which it is connected to the pins, and thus collides against one of them, in particular in the previously identified second contact point. Such a collision causes the emission of a noise, known as knock, which, since it is a collision, triggers vibrations in the braking system which may also energize natural frequencies of the system or of a component thereof, generating annoying vibrations and, above all, noise.
Such a situation is naturally even more critical in the case of successive steps of forward travel-braking-reversing-braking, and vice versa, because multiple collisions occur alternatively against the two supporting pins which work, in turn, as relieving pin of the braking action. As known, knock causes low comfort of the vehicle on which the brake caliper is installed, particularly in the case of high performance and luxury vehicles.
For example, documents EP-2746612 and WO-2010-010583, by the Applicant, and document US-2015-041259 show symmetric or specular pad solutions comprising eyelets having particular shape, entirely similar as a “D”, adapted to reduce the aforesaid knock phenomenon. According to these disclosures, the knock phenomenon is reduced by increasing the number and improving the distribution of the contact points between pins and walls of the pad eyelets. The symmetric or specular configuration of the eyelets on the pad allows a conforming behavior both in forward travel conditions and in reversing conditions.
Such solutions, although partially advantageously, have some drawbacks.
Indeed, such known eyelets are inappropriate to both work simultaneously to determine a reduction of the tangential acceleration of the pad with respect to the pins. In other words, in such conditions, the pad relieves in all cases the entire tangential component of the braking action solely by means of the contact between the eyelet arranged on the inlet side of the brake pad and its respective pin.
The need is thus strongly felt to solve the drawbacks of the prior art mentioned herein.
At the same time, the need is felt to provide a brake caliper solution for brake disc capable of applying a quieter braking action with respect to known solutions, both in forward driving conditions and in reversing conditions of the vehicle.
Solution
It is an object of the present invention to devise a solution for the needs expounded with reference to the prior art.
It is a further object of the present invention to suggest an improved pad type for brake disc caliper capable of providing an optimized relieving action, from the pad to the pins, of the forces and stresses which occur during braking.
It is a further object of the present invention to provide a brake disc for a vehicle brake disc adapted to perform quiet braking, or quieter braking than the known solutions, both in forward travel conditions and in reversing conditions of the vehicle.
These and other objects are achieved by a pad according to claim 1, an assembly according to claim 7, a brake caliper according to claim 9, and a method according to claim 10.
Some advantageous embodiments are the subject matter of the dependent claims.
According to an aspect of the invention, the provision of asymmetric or non-specular slots on the supporting plate of the pad having a specifically designed profile allows an optimal distribution of the tangential components of the forces deriving from the braking action between the pads and both pins at the same time.
By virtue of the simultaneous tangential biasing of both supporting pins of the pad, it is possible to cancel or at least strongly mitigate, with respect to known solutions, the accelerations between pads and pins responsible for the knock phenomena due to collisions between the slot walls and the respective pin.
According to an aspect of the invention, a pad comprises mutually different slots, said pad having non-specular profile and said slots being specifically shaped to bias in tangential direction both pins simultaneously, said pad is adapted to provide the contact between each pin and the respective slot walls during the braking action continuously and without interruption, thus resulting inappropriate to allow the detachment between pins and pad while guaranteeing an assembly with clearance of the pad of the pins to allow them to slide axially, when moved by specific thrust means.
FIGS. 6 to 8 are front view diagrams of an assembly comprising a pad and two pins, according to a first embodiment, which show different steps of braking, in forward travel conditions of the vehicle;
FIGS. 9 to 11 are diagrammatic front views of an assembly comprising a pad and two pins, according to a first embodiment, which shows different steps of braking, in reversing conditions of the vehicle;
FIG. 12 is a front view of a pad, according to an embodiment;
FIGS. 13 and 14 are enlargements of the portions shown by the arrows XIII and XIV in FIG. 12, respectively;
FIGS. 13bis and 14bis are further enlargements of the portions shown by the arrows XIII and XIV in FIG. 12, respectively.